As a display device such as a display device of a thin-screen television or a personal computer, or a small display device for a cellular phone or a smart phone, an active matrix liquid crystal display device which uses a thin film transistor (TFT: Thin Film Transistor) as a switching element is widely utilized. In addition to conventional TN liquid crystal display devices, other types of liquid crystal display devices such as liquid crystal display devices utilizing a VA (Vertical Alignment) mode as a vertical alignment mode or an IPS (In-Plane-Switching) mode as a horizontal electric field mode have been developed.
As a liquid crystal display device of VA mode, a liquid crystal display device of MVA (Multi-domain Vertical Alignment) mode, a liquid crystal display device of CPA (Continuous Pinwheel Alignment) mode, and the like are known. In the liquid crystal display device of MVA mode, multiple domains in which orientation directions of liquid crystal molecules are mutually different are formed in one pixel. In the liquid crystal display device of CPA mode, orientation directions of liquid crystal molecules are continuously varied around a rivet or the like formed on an electrode in the center portion of a pixel.
For example, Patent Document No. 1 describes a liquid crystal display device comprising a plurality of projecting structures in a pixel region and operating in a VA mode. The projecting structures disposed in the pixel region are utilized for regulating the orientation of liquid crystal molecules. Part of the projecting structure also functions as a columnar spacer used for maintaining a cell gap (the thickness of a liquid crystal layer).
Patent Document No. 2 describes a liquid crystal display device of MVA mode in which many minute slits (cuts) extending in directions of azimuth angles of 45°, 135°, 225°, and 315° are formed in a pixel electrode (also referred to as a comb-like pixel electrode or a fishbone-shaped pixel electrode). The azimuth angles are angles measured by regarding the three o'clock direction as 0° and regarding the anti-clockwise direction as a direction of positive angles. The liquid crystal molecules are aligned in parallel to these slits, thereby realizing four-divided domain structure. Patent Document No. 3 describes a semi-transmissive liquid crystal display device which can operate in the MVA mode.